Gestational diabetes mellitus is defined as “glucose intolerance resulting in hyperglycemia of variable severity with onset or first recognition during pregnancy.” This excludes a mother’s pre-existing type 1 and type 2 diabetes and only considers what develops during the second and third trimesters of pregnancy. Around 14% of pregnancies are affected by gestational diabetes mellitus worldwide. Gestational diabetes mellitus, although observed during pregnancy, can have lifelong impacts on the health of both mother and child. Hence it is imperative to identify deranged glucose metabolism and diabetes during pregnancy and treat it effectively.
Pathophysiology
To understand the pathophysiology of gestational diabetes mellitus, it is essential to first know about changes in the levels of insulin sensitivity during gestation. In the early stages of pregnancy, insulin sensitivity increases to the storage of adipose tissue in a mother, which can be utilized for the excess energy demands of later stages of pregnancy. But gradually, insulin sensitivity declines due to the effects of hormones. This occurs to fuel the energy needs of the growing fetus. After pregnancy, all these changes return to normal. In a few cases, the above-mentioned adaptive changes do not occur as expected, leading to gestational diabetes mellitus. Beta cell dysfunction and chronic insulin resistance are the main causative factors for developing gestational diabetes mellitus.
What are the risk factors involved in gestational diabetes mellitus?
Some risk factors contributing to gestational diabetes mellitus are obesity, increased weight gain during pregnancy, western diet, ethnicity, increased maternal age, family or personal history of gestational diabetes mellitus, and polycystic ovarian syndrome.
What complications may arise due to gestational diabetes mellitus?
As mentioned earlier, gestational diabetes mellitus can lead to several health repercussions. In a mother, it can lead to antenatal depression, preeclampsia, preterm birth, increased chance of caesarian section, type 2 diabetes mellitus, and cardiovascular disease later in life. In a child, it can cause macrosomia, hypoglycemia after delivery, stillbirth, obesity, type 2 diabetes mellitus, and cardiovascular diseases. A female child can also develop diabetes during pregnancy; hence a vicious intergenerational cycle of gestational diabetes mellitus develops.
How can gestational diabetes mellitus be diagnosed and screened?
Pregnant women are divided into low, average, and high-risk categories and should be screened accordingly. The low-risk group includes pregnant women less than 25 years old, low-risk ethnicity, absence of diabetes in first-degree relatives, no personal history of abnormal glucose levels, normal pregnancy weight gain, and no prior poor obstetrical outcome. This group requires no blood glucose screening. The average risk group that falls neither into the low nor high-risk category requires screening between 24-28 weeks. The high-risk group, which includes childbearing women with marked obesity, diabetes in first-degree relatives, personal history of glucose intolerance, and current glycosuria, requires blood glucose screening at the initial antepartum visit and 24-48 weeks.
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Once diagnosed, treatment in the form of dietary advice, physical activity, blood glucose monitoring, and insulin therapy should be commenced to reduce perinatal complications and improve quality of life. Diet and exercise are key to controlling glucose levels in pregnancy. They have also been proven to lower the risk of progression of gestational diabetes mellitus to type 2 diabetes mellitus later in life. Despite these measures, subcutaneous insulin therapy is advised if optimal glucose tolerance is not achieved. Insulin is, however, relatively expensive, and difficult to administer. Metformin is now considered safe to be used in pregnancy, either alone or combined with insulin, and is much more compliant.
